1. Why does `apply_patch_dir nonexisting_dir` not return an error?
2. Why does it always use -fp1?
- I never use -f … it still fails if the patch doesn't fit, right,
especially if it doesn't find the file to patch?
- Why not -N, too?
- Is p1 always the correct parent length? That should be mentioned as a
prerequisite for patch dirs.
- Why not support more arguments to specify the patch mode to use?